Downdraft-kiln.



No. 640,246. Patented Jan. 2, I900. H. A. WHEELER.

DDWNDHAFT KILN.

(Application filed. Mar. 27, 1899.)

2 Sheets Sheet 1.

(No Model.)

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No. 640,246. Patented Jan. 2, 1900. H. A. WHEELER.

DUWNDRAFT KILN.

(Application filed Mar. 27, 1899.)

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HERBERT ALLEN lVI-IEELER, OF ST. LOUIS, MISSOURI.

DONDRAFT KlLN.

SPECIFICATION forming part of Letters Patent No. 640,246, dated January2, 1900.

Application filed March 27, 1899- Serial No. 710,683. (No model.)

To all whom it may concern:

Be it known that I, HERBERT ALLEN XVHEELER, a citizen of the UnitedStates, residing at St. Louis, in the State of Missouri, have inventednew and useful Improvements in Downdraft-Kilns, of which the followingis specification.

My invention relates to improvements in downdraft-kilns that can beoperated as a semimuffie-kiln for burning brick, tile, terracotta,sewer-pipe, pottery, and other wares that require burning; and theobjects of my invention are to secure much greater uniformity in theware burned in the kiln, to reduce the time and labor in burning, toeconomize in fuel, and to reduce the cost of construction andmaintenance of the kiln; and with these objects in view my inventionconsists of the novel process and combinations hereinafter described andspecifically set forth.

In the downdraft-kilns now in common use, in which the heat and gasesfrom the fireboxes rise through bags or flash-wall passageways up thesides to the top of the kiln and thence down through the ware to aperforated floor or open bottom, from whence they are led away by finesto one or more chimneys or stacks, there is a great difference in thetemperature between the top and bottom of the kiln, and consequently inthe quality of the ware, so that if the ware in the upper portion of thekiln is properly burned the ware near and at the bottom is usually toosoft and has to be reburned again, or if the kiln is run long enough tosecure well-burned ware in the bottom of the kiln the top of the kiln isusually spoiled bybeingoverburned. While great skill in burning theusual downdraftkilns may reduce the loss from overburned to underburnedware, it still requires a prolonged time, with an excessive cost forfuel and labor, and there is still such a marked difierence in thequality of the ware between the top and bottom of the kiln as to requirecareful sorting into difierent grades or shades. This difficulty arisespartly from the poor heat conductivity of clay goods, but mainly fromapplying the heat only at the top of the kiln and then drawing it downto the bottom of a kiln of ware that may be from six to sixteen feet inthickness, by which process the ware at the bottom of the kiln Where theheat escapes must manifestly be much cooler after passing down through athick body of clay goods than at the top of the kiln. In my improvedkiln I employ a new principle or process, the semimuiiie process, inwhich the heat is first applied at the bottom before it passes to thetop, so that the ware is heated equally from both top and bottom at thesame time, and hence the great trouble of underburned ware in the lowerpart of the kiln or overburned Ware at the top of the kiln is eliminated, While a great saving in time, fuel, and labor results inconsequence of the heat entering the ware from both the bottom and topat the same time. Furthermore, in applying this new process of heatingthe bottom by means of under-bottom flues a solid tight bottom or flooris employed, which materially lessens the cost of construction andoperation of the usual perforated or open-bottom kiln, as the specialfloor-tile are no longer necessary, which constantly break in use andnecessitate frequent cleaning out of the fines from the sand and dirtthat falls through the open ings in the floor and clogs up the dues. I11applying the heat first along the bottom of the kiln the escape-Hues forthe discharge of the gases are placed at a distance or horizon of, say,one-third to one-half the depth of the ware, more or less, in either theside walls or end walls of the kiln, above which escapeports the ware isheated by direct contact with the heated gases, whereas the ware belowthese escape-ports is not thus heated, but receives its heat, as in amufiie-kiln, by radiation from the hot floor mainly and to a slightextent by the hot flash-walls. Thus the lower portion of the kiln isheated 011 the muille principle, as to all intents and purposes it is amuffle below the escape -flues, whereas above the escape-fines the kilnoperates on the usual downdraft principle by the heated gases passingthrough and coming in direct contact wit-h the ware.

In previous efforts to heat the floor of downdraft-kilns theescape-fines have been placed in the end walls at the bottom of thekiln, by which the value of the hot bottom was largely lost by theescaping gases passing along the heated floor on their way to theescape-fines in the end walls, thus carrying the heat from the hot floorout of the kiln and wasting it, as well as nullifying the benefit ofheating the bottom. Furthermore, by having the escape-fines in the endwalls the kiln cannot be of more than moderate length or the centralportion of the kiln will not be hard-burned, whereas in my system ofplacing the escape-fines in the side walls the length of travel for thegases is always short, and hence the kiln can be of any length or onehundred feet or more, as in brick-kilns.

In the accompanying drawings I have shown the improvements applied toboth a rectangular and a round design of kiln, as it is applicable toeither.

Figure 1 is a horizontal section through the under-bottom flues on'theline II II, Fig. 2 is a horizontal section through the escapeflues onthe line III III, and Fig. 3 is a vertical cross-section through afire-box on the line I I, of a rectangular kiln. Fig. 4 is a horizontalsection on the line V V, Fig. 5 is a Vertical section on the line IV IV,and Fig. 6 is a vertical section on the line VI VI, of a round kiln.

Similar letters refer to similar parts in all the drawings.

A and B are the fire-boxes or furnaces in the side walls X X, and Y Yare the end walls,

of the kiln. The backs of the fire-boxes or furnaces B open into thefire-fines cl between the fiue-wallsp, that pass under the solid bottomor tight fioor 7a to the opposite side of the kiln d, whence the heatand gases rise up, through the passage-ways l between the side walls Xand the flash-wall f, to the top of the kiln, as shown by the longarrows, while the heat of radiation and conductivity that passes throughthe solid floor up into the ware in the lower or muffle portion .of thekiln is shown by the short arrows.

The heat and gases pass down through about two-thirds of the ware to theside or escape fines 11, which connect with the chimneyfiues g andescape into the air by the stacks j. Similarly the furnaces A dischargeinto the fire-fines c, which pass under the tight floor Z: to theopposite side of the kiln c. Thence the heat and gases rise up,throughthe passage-ways Z, to the top of the kiln, and thence down, throughmore than half of the ware, to the side or escape fines 2", that openinto the chimney-fiues g in the stacks or chimneys j.

The side fines t' t" through the flash-wallsf f into the chimneyfines gg are carried across the space Z l by Roman brick or tiles or anysuitable material it h for spanning these passage-ways.

The bottom fines O O, that pass from the furnaces A to the opposite sideof the kiln, and the bottom flues d d, that pass from the furnaces B tothe opposite side of the kiln, or I in alternate directions, completelyunderlie the entire bottom of the kiln 7c, and thus insure its thoroughheating to the same degree as the top of the kiln. These bottom finesare tightly and completely covered by ordinary fire-brick or Roman brickor tiles, as may be found preferable for given conditions, which are setsolidly or tightly against one another, or what is known in the trade asa solid floor,without leaving any slotsor slits or openings, as is donewith ordinary downdraft-kilns, and which is known in the trade as anopen or perforated fioor. These latter openings through the open floorsare obtained by leaving spaces of one-fourth to one-half inch or sobetween each tile or brick or else using tile or brick made with specialslots or openings, which openings allow the passage of the gases andheat through the floor and also admit the falling of sand, dirt, andrubbish through the floor into the fiues below when the kiln is beingfilled or emptied. The solid or tight bottom that I employ prevents thepassage of the gases through the floor and also prevents the fouling ofthe fines underneath from sand, dirt, &c.

The illustrations are shown with the furnaces A and B opposite oneanother or vis-avis in the rectangular kiln, as is the usual arrangementin present kiln practice, and I have selected this condition to showthat my improvements can be readily adapted to kilns now in use. This,however, necessitates carrying the bottom fiues obliquely across thekiln, as shown, and in order to secure a hot bottom in front of the doorW and the corner O O of the kiln the flue C C opens by ports orpassage-ways e 6 into the fiue O and this flue opens by the port e intothe fine 0 thus returning the heat and gases to the corner 0 O and sosecuring a complete heating of the entire bottom.

Where a kiln is specially built with my improvements, it will be moreconvenient to build the furnaces staggered or alternating instead ofopposite to one another, as is shown in the round kiln, Fig. 4, whichwill enable the bottom or fire fines to be carried straightacross thekiln in a rectangular design instead of obliquely, as shown, and todispense with the special arrangement shown of the corner-fines C O C Cand the arrangement illustrated is shown to demonstrate that myimprovements can be equally as well applied to the old kilns now in useas to new ones. In the round kiln it is preferable to arrange the bottomfines of the side furnaces obliquely, as shown, or else in a curveddirection, to carry the heat under the bottom near the sides Y Y onaccount of the shape of the round design of kiln.

While each furnace is shown as opening into three bottom fiues in therectangular kiln and into two fiues in the round kiln, the number ofthese fiues per furnace can be varied to suit given conditions or fromone to three or more per furnace.

The particular distance of the side or escape fiues t t" above the floorwill vary according to the detail design and use of a particular kiln,as the thinner the floor-bottom the higher IIO ea aae a up the radiatedand conducted heat through the floor will pass, and consequently thehigher up should be placed the side dues, and the higher a kiln is setthe higher up'should these side fiues be placed, as some wares are onlyset as high as the flash-walls or bags, while other wares are set to thecrown of the arch. In general it will probably be found that aboutone-third of the height of the side walls is the place where the heatarising from the bottom will burn the ware as hard as that burned by theheat conveyed down from the top of the kiln through the ware by theheated gases, or, in other words, the lower third of the kiln, more orless, will be practically a muffle or burned on the muffle principle,whereas the upper portion will be burned by direct contact with theheated f urnace-gases.

The illustrations show the fiash wall type of design for forming thepassage-way for the gases from the bottom to the top of the kiln alongthe side walls; butif the bag or pocket system is preferred it can'beeven more favorably employed, and the side fiues t' t" then become mereport-holes in the side walls between the bags for the escape of thegases into the chimney-fiues g g, and the bridging brick or tile h h arethen no longer necessary.

The furnaces A and B are shown to be of the downdraft solid-bottom type,in which the air passes down through the neck or firing-hole m of thefurnace as well as through the ash-pit arch 91., while the fuel rests onthe solid bottom 0. This type of furnace is very simple and economicalin construction and maintenance, is very economical in fuel, and issmokeless; but any other design of furnace as may be found preferablecan be used.

To enable the gases to reach the side lines 2' i, the ware is so set inthe kiln as to leave open spaces or small fiues through the ware thatcommunicate with the side or escape fiues i 2'.

Where rectangular kilns now in use do not have side stacks built intothem, the chimneys can be built on the outside of the kiln against theside walls, being ,held against the side walls by the usual sidebracing, or they may be built in the corners of the furnace or in theend walls where the kilns are not too long to successfully burn thecentral portion of the kiln.

In round kilns the diameter is rarely, if ever, too large to prevent thesuccessful use of the arrangement shown, and in applying my improvementto old kilns the chimneyfiues can either be built inside or outside ofthe side walls, though in new kilns it will be found more economical tobuild them within the side walls.

By using a solid or tight bottom the cost of construction andmaintenance of the kiln is materially reduced under the present practiceof using an open or perforated floor, as the extra expense of thespecial brick or tile required for the perforated bottom, their frequentbreakage, the necessity of protecting them with planking each time thekiln is emptied, and the filling up of the fiues from sand, dirt, &c.,that fall through the perforations is entirely avoided by making thefloor a smooth, continuous, solid bottom out of common sizes of brick ortile. The thickness of these floor-bricks can be varied to suit thelocal conditions.

I have shown the furnaces as being located on both sides of the kiln,whichresults in the heat and gases traversing the bottom fiues inalternately opposite directions, and thus insures an equal heating ofthe entire bottom of the kiln; but the furnaces can be all located onone side of the kiln, if preferred, though generally this arrangementwill not be found satisfactory for equalizing the heat, which latter isusually such a very important feature in the successful burning of mostwares.

hat I claim, and desire to secure by Letters Patent, is-

In a downdraft-kiln, the combination of under-floor fiues with a solidbottom, the transverse fiues 0 C the return corner-fiues C and O,openings 0 from C C to 0 openings c from C to O, with escape-fiueslocated above the floor, substantially as shown.

HERBERT ALLEN WHEELER.

Witnesses:

HUGH K. WAGNER,

RALPH KALISH.

